Spring structures



N. A. CRITES SPRING STRUCTURES Fil'ed May 28, 1953 July so, 1957 INVENTOR Nelson A. Crijes 5 7 I MA 9W7] ATTORNEYS.

United States Patent SPRING STRUCTURES Nelson A. Crites, Columbus, Ohio, assignor, by mesne assignments, to Standard Steel Spring Company, Coraopolis, Pa., a corporation of Pennsylvania Application May 28, 1953, Serial No. 358,058

1 Claim. (c1. 267-49) This invention relates to polyethylene coated steel prodducts, and, in particular, to polyethylene coated steel leaf-spring structures.

It has long been the object of improvements in the spring manufacturing art, to obtain springs which are quieter in operation with a minimum of maintenance and lubrication. Longer spring life has been a further goal sought in this art.

Interleaf spacers have been used to produce quieter operation, with varying degrees of success. The use of interleaf spacers has produced quieter operation, but has brought with it the problems of matching the spacer life with that of the spring. Interleaf spacers of the usual materials, such as either wood, pressboard, canvas impregnated or covered by grease, or other similar lubricant, or soft bearing metals have deteriorated under the constant rubbing action which takes place between the leaves of the spring structure while in use. This deterioration has been further accentuated by the shifting of the spacer responsively with the rubbing action.

Various types of external sheaths have been employed to cover the edges of spring structures for the purpose of protecting the edges of the steel spring leaves from corrosion. This has been considered of importance to spring life, as it is along these highly stressed edges that corrosion causes weakness, which in turn leads to early spring failure.

An object of this invention is to provide a spring struc ture with interleaf spacers which do not shift during interaction between the spring leaves, thus prolonging interleaf spacer life.

Another object of this invention is to provide a spring structure with interleaf spacers which will cover the edges of the spring leaves, thus prolonging spring life without the use of external sheaths.

Still another object of this invention is to provide spring structures with interleaf spacers which will have a life equal to the spring life with which they are used.

A further object of thisinvention is to provide a spring structure with interleaf spacers which will operate quietly without lubrication and with greatly reduced maintenance care.

Other objects and advantages of the present invention will become apparent from the following detailed description thereof, when read in conjunction with the accompanying drawings, in which:

Fig. 1 is a side elevation view of a typical leaf-spring structure;

Fig. 2 is a sectional view taken along the line 2-2 in Fig. 1;

Fig. 3 is a side elevation view of a typical leaf spring; and

Fig. 4 is a sectional view taken along the line 44 in Fig. 3.

In the past, spring structures have been built in many shapes and having varied constructions. The structure which forms the preferred embodiment of this invention, as shown in Figs. 1 and 2, is that type which is composed 2,801,100 Patented July 30, 1957 of elliptically formed steel plates or leaves 5, placed one upon another, usually decreasing in length respectively from a main plate 6 progressively to a short plate 7. The main plate 6 usually has a pair of eyes 8 at its ends for attachment to a frame member, not shown; and the structure is usually clamped by a U-bolt means 9 to an axle member, not shown, which is in contact with short plate 7. Each leaf has edges 10, which appear as corners in Fig. 2, and are usually rounded. A familiar example of this type of spring structure is the one being used to support the rear axles of present-day automobiles.

In the most common practice of the spring manufacturing art, spring leaves are substantially rectangular in cross section taken perpendicular to the longest dimension. In many instances, the rectangular shape is modified, to some extent, to obtain certain desired operational characteristics. These cross-section modifications may be in the form of cut-out portions, as the result of grooves running longitudinally. The cross-section may have a parabolic edge contour. that in the most common practice, the cross section remains substantially rectangular, even though modified.

Persons acquainted with the art are familiar with the concept that one side of the spring leaf will be in tension when the spring is fiexed, and the opposite side will be in compression. which refers to one side as the normally tension side and the opposite side as the compression side. The term normally is used because in some cases prestressing of polyethylene, which is securely bonded to the steel spring leaves and to spring leaves which have a coating of polyethylene securely bonded thereon.

In Figs. 1 and 2, a spacer 11 is shown comprising a layer of polyethylene bonded to a tension-side surface 12 of spring leaves 55 and 7. The spacer 11 is continued around the edges 1010 and down the sides 13-13 of the spring leaves and bonded thereto.

The polyethylene layer is continued the full length of each spring leaf. On the leaves 5-5 and 7, at each end 14, the layer may be extended around the end edge 15 and down the end surface 16 far enough to produce an effective bond.

Figs. 3 and 4 show a single leaf 17 coated with a layer 18 of polyethylene according to this invention. The layer 18 is bonded to the spring leaf 17 in the same manner as previously described for a leaf of the spring structure, except at each end 19, where it is terminated close to eyes 20.

This single leaf may be used alone or a similar leaf may be used as a main leaf of a spring structure composed of multiple leaves. In either case, the advantage of protection against corrosion is provided.

lnterleaf spacers of polyethylene are resistant to acid, alkalies, and water; are not atfected by temperature within the range of normal atmospheric conditions, and are extremely tough and resistant to abrasion by rubbing of the spring leaves on each other during spring operation. When continued around the edges and down the sides, the spacers protect these surfaces from corrosion.

As a further advantage, these spacers are quiet when exposed to sliding friction forces. Although it is not known why, it has been established that springs coated as disclosed in this invention will not squeak in operation when used without external lubricants. Since it is known that the coefiicient of friction between steel and polyethylene is high, compared with many other spacer materials on steel, it is supposed that the vibrations, if any, produced by the rubbing action between the polyethylene and the steel leaf at the unbonded contact line 21 are However, it will be understoodv From this has come the terminology not of 'normalaudio frequency. Thus, although it cannot'be said"th'at the interleaf "spacers of 'this" invention are self-lubricating, for practical purposes the etfect is vide's added strength and 'supportlwhichxhelps the, coat: in'g to ,withsta'ndthe normal :interspring rubbing, action; The bondreferrd ,to, above ,is t ilerefie'ctive fusion of thfej steel surface .-:with the surface. of. the polyethylene. layer. The-strength, of-j adherencegachieved, is great enough that thepolyethyleneisreinforced 'by the; greater.

tensileustrengthlof,thezsteele. Therm'ethod .oflachieving' this, bbndjisidescrihedgima' copending application en-.

' titledI.M thOd andAPP iratus. for :Coating. Springsj. Serial. No, 352,540,1 filed- May .1,, 19:53. It.-comprises ap plying-g anlayer, of polyethylene-at, a, temperature oi 500I6l5 F.-to -steel..at.a.temperaturesof 3 50 60()- F. T he. materials bondtogether. at their surfaces of contact, causinguthelayerjto adhere .to the steel.-

.A problem Which is:cmmon-in the prior art is keeping. V This problem has: been :met: bythe. use of clips andcovers- The present inthetlooseinterleaf spacers in place.

ventibnsolves :this problem without the 'useof clips and covers, as the bond prevents the spacers from slipping out.

Spring structures have been manufacturedaccording to..this invention and have fulfilled the purposes; herein setzforth; For example, an automobile springstructure wasmadehavingpolyethylene interleaf spacers MO-inch thick This structure was .tested on a spring-flexing:

machine. 7 V V Thismachine consists of means forrholdin'gnthe spring structure byits eyesin a similar manner :as under an 7; automobile, and'means for mechanically grippingethe;

structure at its center point and moving this center-ups:

and down. The motion-of the'center simultates. the, action;

ofa spring structure during normal operationiof the auto.-

mobileonthe highway: In this machine, the-amount :of 1 7 travel performed. by the center point jlIiOIlQadiIfiCiiOIliiS.

considered a-stroke', A cycle is zdefinedr'as two:strokes,f

i. e., one up and one rdownitonormal position;

In the example rtest,1 the;str oke washset .atrS inches,

21 fram,e;--stop;-

failure; Thespacers indicated a maximum of .010.-inch wearqat the:.pressurelpoints, which is wherethe spacer at lheeleafiend'ntub's theleafahover;

The:MaIiual ofiD'esign-and Application of Leaf Springs;

War.:En'gine.e1iJJg.-t(l944), publishedby' the Society of Automotive Engineers states at page 77 that 100,000 full- L load;cyclesron a flexing machineis equivalent to. 100,000

whichis, equivalent tohavingtheautomobilte :wheel strike;

milesr of-lautomobilelhighway travel. It isseen-that the- I 4 V 7 structure of the above example performed well beyond the normal life of an automobile, and the spacer has an equal life. 7

Other test spring structures according to this invention have shown similar results. The thickness of the layer has been varied between .020 inch and .060 inch and there has not been any changein the result. It is believed that the thickness of'thelayerwis'not a determining factor in the successful practice of this invention, pro

vided it is thicker than theamountofwear.

Thus, it is seen" that thisinvention'providesra-"spring structure which is quiet in operation andwhich' has interleaf spacers which will have a life substantiallyequal to the life of the'spring structure. p

In the spring structure ofthis invention, the interleaf spacer provides a corrosion-proof cover for the spring-. leaf edges and which will protect these highly stressed edges from corrosion, thus increasing .1spr ilife; by; preventing failure at these criticalpointse, j I

While the form of the embodiment of;the; present;:i1r:;-' vention herein disclosed'. constitutes a preferrcdiform,; it is to be understood that other forms might. iberadoptedg. all coming within the spirit of ,the.'invention:,

Whatt'is claimed is: V 7 9 g A multiple-leaf spring structure comprisingasuperposed steel spring; leaves, each substantially rectangular :irimross section, taken perpendicular :to :its longest-dimension; and;

substantially parallel to each; other,'-'. andnpt'alyethylene'- interleaf spacers inthe spaces @between .zadjacentaleaves each said polyethylene spacer being zsecurely: bonded :by

surface fusion at elevatedrtemp er'ature .-'to,,1the.s1-tension-; sidesurface of the adjacent.leaf;that.has'itsztensionside contiguous to saidjspacer and. to. portions of the sidesand ends-of said leafborderingon:saidstension-sidesurface, said polyethylene. spacer being :in 'sliding engage ment with: the compression-side Sul'ffiCfigOf the, otheradjacent leaf, and'saidspacers serving-aswear-preventing} bearing members between adjacent leaves and at the -same' time as corrosion-preventing films o11 said tension-side surfaces of said leaves.

References Cited in the tile of this patent 2,

UNITED STATES PATENTS Re. 14,870 Hamilton ...June. 1,1 1920] 1,967,088" Geyer Ju1y 17,' 1934:1 2,643,955 Powersetal. June 30,1953 2,649,297 Dow... Aug. 18,.,1 9 ,53- 2,666,637 Lindeman s r Jan.,1-9,;195.431 2,667,347" Jacobs ..Jau.;26,*= 19,54:

FOREIGNJATENTSF or r 571,867 Great Britain S'ept. 12,,19453 602,420; Great Britain May..2 6,i,.1948 

